1. Field of the Invention
The present invention relates to a near infrared absorption composition and a near infrared absorption filter produced from the composition. More particularly, the present invention relates to a novel near infrared absorption composition which shows an absorption for a near infrared region and a high transmittance for a visible light region and wherein attention has been paid to environmental problems; as well as to a near infrared absorption filter produced from the composition.
2. Description of the Prior Art
In recent years, development of plasma display panel has been active and its products have been put into market. As is easily anticipated from their principle, plasma display panels emit a near infrared light during the plasma discharge; since this near infrared light is close to the near infrared light used by the remote controllers of electronic appliances such as household TVs, air conditioners, video tape recorders and the like, plasma displays invite malfunctioning of the electronic appliances placed in the vicinity thereof. Hence, a near infrared absorption filter is often used as a surface plate of plasma display, for absorption and shielding of a near infrared region of 800 to 1,000 nm, particularly 850 to 1,000 nm.
The above near infrared absorption filter has been produced in various forms and there are being actually used, for example, a filter comprising a glass as a filter substrate and a metal (e.g. silver) vapor-deposited on the glass for reflection of near infrared light, and a filter which is an appropriate transparent polymer containing a near infrared-absorbing dye. However, the former filter requires large production equipment, resulting in a high cost; and the latter filter has absorptivity also for a visible light region, resulting in lower transmittance for visible light.
A filter which is an appropriate transparent polymer containing a copper salt of carboxylic acid, is also provided. In general, copper salts of carboxylic acid such as copper acetate, copper stearate and the like have low solubility in solvents by themselves. Therefore, it is difficult to allow a copper salt of carboxylic acid to be present in a transparent polymer at a high concentration; further, a copper salt of carboxylic acid shows the maximum absorption at around 700 nm and accordingly is unable to show sufficient absorptivity for near infrared light. Therefore, it is necessary to add phosphoric acid, thiourea or the like to the copper salt of carboxylic acid to shift the absorption spectrum to a near infrared side and also is necessary to improve the copper salt of carboxylic acid""s solubility in solvent.
Organic phosphoric acids are designated as a hazardous industrial waste and their adverse effects on environment need to be taken into account. Meanwhile, a near infrared absorption filter which is a transparent polymer containing thiourea, has low absorptivity for near infrared light.
The present invention aims at alleviating the above-mentioned drawbacks of the prior art and providing mainly (1) a novel near infrared absorption composition which has an absorptivity for a near infrared region and a high transmittance for a visible light region and wherein attention has been paid to environmental problems and (2) a near infrared absorption filter produced from the composition.
The present invention provides the following inventions.
[1] A near infrared absorption acrylic composition containing a sulfonic acid group-containing (meth)acrylic compound represented by the following general formula (1):
R(CH2)nSO3Hxe2x80x83xe2x80x83(1) 
(wherein R is CH2xe2x95x90CHCOOxe2x80x94 or CH2xe2x95x90C(CH3)COOxe2x80x94, and n is an integer of 1 to 8), other (meth)acrylic compound and Cu2+.
[2] A near infrared absorption acrylic composition containing a salt of sulfonic acid group-containing (meth)acrylic compound, represented by the following general formula (2):
[R(CH2)nSO3xe2x88x92]2Cu2+xe2x80x83xe2x80x83(2) 
(wherein R is CH2xe2x95x90CHCOOxe2x80x94 or CH2xe2x95x90C(CH3)COOxe2x80x94, and n is an integer of 1 to 8) and other (meth)acrylic compound.
[3] A near infrared absorption resin composition which is a polymer solution containing a salt of sulfonic acid group-containing (meth)acrylic compound, represented by the following general formula (2):
[R(CH2)nSO3xe2x88x92]2Cu2+xe2x80x83xe2x80x83(2) 
(wherein R is CH2xe2x95x90CHCOOxe2x80x94 or CH2xe2x95x90C(CH3)COOxe2x80x94, and n is an integer of 1 to 8).
[4] A near infrared absorption salt of sulfonic acid group-containing (meth)acrylic compound, represented by the following general formula (2):
[R(CH2)nSO3xe2x88x92]2Cu2+xe2x80x83xe2x80x83(2) 
(wherein R is CH2xe2x95x90CHCOOxe2x80x94 or CH2xe2x95x90C(CH3)COOxe2x80x94, and n is an integer of 1 to 8).
[5] A near infrared absorption filter containing the near infrared salt of sulfonic acid group-containing (meth)acrylic compound, set forth in the above [4].
[6] A near infrared absorption acrylic resin plate produced, by thermal polymerization, from the near infrared absorption acrylic composition set forth in the above [1] or [2], and a near infrared absorption filter comprising the near infrared absorption acrylic resin plate.
[7] A near infrared absorption acrylic resin film produced, by UV polymerization, from the near infrared absorption acrylic composition set forth in the above [1] or [2], and a near infrared absorption filter comprising the near infrared absorption acrylic resin film.
[8] A near infrared absorption resin film produced, by casting, from the near infrared absorption resin composition set forth in the above [3], and a near infrared absorption filter comprising the near infrared absorption resin film.
Incidentally, the Cu2+ in the above near infrared absorption acrylic composition [1] is added in the form of, for example, a carboxylic acid salt.